[PATCH v3 2/2] ALSA: usb-audio: test EP_FLAG_RUNNING at urb completion

From: Ioan-Adrian Ratiu
Date: Wed Jan 04 2017 - 17:37:32 EST


Testing EP_FLAG_RUNNING in snd_complete_urb() before running the completion
logic allows us to save a few cpu cycles by returning early, skipping the
pending urb in case the stream was stopped; the stop logic handles the urb
and sets the completion callbacks to NULL.

Signed-off-by: Ioan-Adrian Ratiu <adi@xxxxxxxxxx>
---
sound/usb/endpoint.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 2f0ea70a998c..c90607ebe155 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -384,6 +384,9 @@ static void snd_complete_urb(struct urb *urb)
if (unlikely(atomic_read(&ep->chip->shutdown)))
goto exit_clear;

+ if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
+ goto exit_clear;
+
if (usb_pipeout(ep->pipe)) {
retire_outbound_urb(ep, ctx);
/* can be stopped during retire callback */
--
2.11.0